1. Field of the Invention
The present invention relates to a cab suspension system for a truck and, more specifically, relates to a suspension providing lateral location for the cab on the chassis and for restraining the cab from detaching from the vehicle chassis during high acceleration events.
2. Description of the Problem
Vehicle cab suspensions isolate occupants of the cab from shock to and vibration of a truck""s frame. Many proposed suspensions have been characterized by great mechanical complexity, resulting in added maintenance costs, and by excessive bulk, making it difficult to fit the suspension within the space allowed between the cab and the frame. A factor contributing to the size and complexity of some of these suspensions is the need to proved lateral control over cab position relative to the frame. In addition, some suspensions have required separate components to provide a restraint against cab detachment in accidents. Lateral positioning has been provided on some vehicles by equipping the vehicles with a lateral tracking or locating link, sometimes called a Panhard rod, between the cab and the chassis. Alternatively, lateral rubbing pads have been provided between cab and chassis which bind when the sprung and unsprung masses roll relative to one another.
In U.S. Pat. No. 6,168,229, vander Kooi et al. proposed an alternative suspension system directed to providing lateral positioning of the cab. This system proposed the use of a square metal tube positioned under the aft section of a vehicle cab. The tube is attached to a chassis cross member and is oriented transversely with respect to the direction of elongation of the vehicle. A rubber encased torsion bar is set through the tube and the cab is attached to the free ends of the bar, extending from the tube""s opposed open ends.
Means must also be provided for preventing cabs from detaching from frames during catastrophic events. Such means have often been provided with by attaching metal straps between the cab and the vehicle""s frame.
According to the invention there is provided a vehicle having a suspended cab. The vehicle has a chassis with elongated side frame rails and cross members connected between the side frame rails. One cross member is provided as a support for the back of a vehicle cab. A cab attachment plate is supported above the cross member and provides an attachment point for the floor of the cab. A pair of air springs is disposed between cab attachment plate and the cross member for supporting the cab. A pair of shock absorbers are attached between the cab attachment plate and the cross member for damping vertical movement of the cab. Lateral positioning of the cab and limits to the vertical travel of the cab are provided by a lateral locating wheel mechanism. The lateral locating wheel mechanism includes a roller attachment bracket which may be mounted upwardly from the cross member. A roller contact bracket is mounted downwardly from the cab attachment plate, with the cab attachment plate providing an upper limit to linear travel defined by the roller contact bracket, which defines a vertical guide in which the roller can move up and down. A roller mechanism is mounted to the roller attachment bracket and through the roller contact bracket. In the preferred embodiment the roller mechanism further comprises a single roller having a relatively rigid core and an overmolded rubber shell shaped spherically to provide a non-linear spring rate upon compression.
Additional effects, features and advantages will be apparent in the written description that follows.